This invention relates to an apparatus for transmission of information by the medium of electrocutaneous stimuli adapted to rouse the cutaneous sensation of a human subject.
For example, transmission of information through the medium of electrocutaneous stimuli has been adopted in a system wherein the operation of a prosthetic hand or manipulator by its operator is facilitated by feeding back the sensation of touch or sensation of force to the operator with the aid of a device adapted to convey feedback signals from the machine to the operator, in a system which provides the blind or the deaf with a substitutive visual or audio sensation and in a system of communication between two or more individuals under environmental conditions which prevent normal communication.
Such transmission of information through the medium of electrocutaneous stimuli is generally effected by emitting signals in the form of pulse trains which carry the information in terms of their frequency of repetition, stimulus-duration-time, the pulse height (in the form of either voltage or current) and pulse width.
In the conventional system of this type for the transmission of information, signals desired to be conveyed are simply converted into corresponding magnitudes of electric current or some other suitable electric phenomenon and are directly presented to the skin. Because of its anatomical nature, the skin is sometimes moistened with perspiration and at other times is dry, causing a frequent fluctuation in the electrocutaneous impedance. This means that the magnitude of sensation roused by a fixed magnitude of electric current, for example, is likely to vary with time and occasion. This variation has posed a problem in that it prevents the information from being transmitted exactly.
An object of this invention is to provide an apparatus for the transmission of information through the medium of electrocutaneous stimuli, which apparatus is capable of enabling any particular signal to rouse a fixed magnitude of sensation at all times.